Aqueous synthesis of Cu-doped CdZnS quantum dots with controlled and efficient photoluminescence
Résumé
We report here a facile, mild and low cost aqueous-based synthesis for the production of high quality CdZnS and Cu-doped CdZnS quantum dots (QDs). We demonstrate that the photoluminescence (PL) of the Cu-doped CdZnS nanocrystals could be tuned in the whole visible spectrum via the stoechiometric ratio of Cd/Zn precursors in the host CdZnS QDs and by tuning the particle size. By optimization of the experimental conditions (Cd/Zn ratio, reaction time, pH,…) and by varying the surface ligand, pure and highly emissive Cu:CdZnS QDs could be prepared. Moreover, by the growth of a ZnS shell around the Cu:CdZnS core, Cu:CdZnS/ZnS QDs with a PL quantum yield (PL QY) of 42% were constructed, which is the highest PL QY reported to date for Cu-doped CdZnS QDs prepared in aqueous solution. The optical properties and structure of the obtained dots were characterized by UV–visible spectroscopy, steady-state and time-resolved PL spectroscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Cu:CdZnS/ZnS QDs were subjected to various treatments such as long-term UV illumination, storage in biological buffers or pH changes, which are usually detrimental to QDs PL. No marked deterioration in PL properties during the previously described degradation processes was observed, thus indicating the high stability of the dots prepared. Due to their good water dispersibility and stability, the Cu:CdZnS/ZnS QDs developed herein can be a promising candidate for biolabelling applications.